1. Field of the Invention
This invention relates to differential pressure forming apparatus and more particularly to transfer apparatus for transferring an article differentially pressure formed in, and trimmed from, a thermoplastic sheet at a form and trim station to a vertically lowered and horizontally displaced discharge station.
2. Description of the Prior Art and Objects
Apparatus, such as that disclosed in U.S. Pat. No. 5,585,689 issued to G. W. Brown, et al on Jun. 22, 1971, and U.S. Pat. No. 4,313,358 issued to Gaylord W. Brown on Feb. 2, 1982, which are each incorporated herein by reference, has been provided heretofore for trimming articles, differentially pressure formed in a thermoplastic sheet, at a trimming station which is downstream of a forming station. U.S. Pat. No. 5,225,213 issued to G. W. Brown and Albert W. Arends on Jul. 6, 1993, discloses apparatus for trimming an article from a thermoplastic sheet including a wedge for incrementally moving a trim die from a remote position to a sheet severing position.
A problem attendant to the machines which trim parts in a thermoplastic sheet is the removal of parts from the mold. One machine which has been provided for removing differential pressure formed parts from the mold includes a vacuum plate, of the type illustrated in U.S. Pat. No. 4,560,339 issued on Dec. 24, 1985 to Pietro Padovanni. This patent discloses the concept of moving a vacuum plate between separated molds, engaging the cups and withdrawing them from the molds. This is a relatively slow, time consuming process.
A problem with this prior art construction which differential pressure forms at an upstream forming station and trims the part from the sheet at a downstream trimming station is the complications resulting from the inability to consistently control the batch to batch chemistry of the plastic. When the articles are transferred to the downstream trim station, the parts may not be precisely aligned with the trim mold to precisely allow accurate trimming. Accordingly, it is advantageous to trim the article "in place" in the mold in order to trim concentrically with the lip of the article being formed.
U.S. Pat. No. 4,170,621, issued to Gunther Keifer on Oct. 9, 1979, discloses forming apparatus having an "in place" trimming machine driven by a cam for trimming parts from a sheet at the mold station. The cutting force required to sever the sheet is rather large and the force exerted by a cam, as disclosed in Kiefer, is sometimes insufficient to properly sever the sheet.
U.S. Pat. No. 4,565,513 issued to Gunther Kiefer on Jan. 21, 1986 discloses apparatus for forming and trimming a part in a thermoplastic sheet at a form and trim station, lowering the lower mold in which a part is formed, tilting the lower platen and mold thereon from a vertical position to a horizontally disposed position, and then ejecting a part into a stacking machine. There are several problems attendant to this construction illustrated in this latter patent including the inability to efficiently and accurately transfer the formed and severed parts to a stacker. Accordingly, it is an object of the present invention to provide new and novel method and apparatus for efficiently and accurately transferring articles, which have been differentially pressure formed in a female mold and trimmed from a thermoplastic sheet while still in the mold from the female mold to a stacker.
Another device for transferring formed parts from a mold at a mold and trim station to a stacker receiver is illustrated in German Publication 1276900 dated Sep. 5, 1968. The construction illustrated in this German publication also is of limited value, however, in that the apparatus only rotates the lower platen and mold thereon and does not bodily move the lower mold horizontally toward the stacker after it is rotated to its lowermost position. It is difficult to transfer the articles in the mold from the mold to the receiver. In this prior construction, there will be a gap between the mold in the rotated position and the receiver stacker. Consequently, due to the great distance through which the article must be propelled to reach the stacker tremendously large ejection force is required to physically propel the articles from the mold through the gap to the stacker. Accordingly, it is an object of the present invention to provide apparatus of the type described which will reduce the ejection forces required to transfer the articles from a differential pressure forming mold to a stacker at a lowered, horizontally disposed stacking station.
It is another object of the present invention to provide transfer apparatus of the type described which will linearly move the mold in a horizontal direction after the mold has moved vertically and after the mold, and article formed therein have been reoriented.
It is yet another object of the present invention to provide new and novel method and apparatus for transferring formed and trimmed articles from a mold and trim station to a stacker and which will move articles vertically away from the mold and trim station and thence will rotate the articles to reorient them to a new orientation, and then move the reoriented parts horizontally to a discharge position disposed in nesting relation with other previously discharged articles.
Another object of the present invention is to provide apparatus which will overcome the problems with the prior art.
It is still another object of the present invention to provide apparatus for transferring formed and trimmed parts having a vertical orientation at a form and trim station to a horizontally disposed orientation at a lower, horizontally displaced discharge station including mechanism for bodily moving the mold and articles thereon in a horizontal direction after the articles have been vertically retracted from the mold and trim station to a lowermost position.
The rotating movement of prior art machines illustrated in the aforementioned prior art U.S. Pat. No. 4,565,513 and the German publication 1276900 imparts a compound motion to the lower mold and trim die. Substantial energy is dissipated to stop the compound motion of the prior art mold and trim die at the stacking station. Accordingly, it is an object of the present invention to provide new and novel apparatus of the type described for efficiently transferring articles, which have been differential pressure formed in and trimmed in place from a thermoplastic sheet, to a vertically and horizontally displaced discharge station.
One of the other problems with the prior art constructions is that the articles, which typically include hollow, then walled plates, cups, and the like are held in the stacker by circumferentially disposed brushes which are intended to grip the circumferential edge but don't always hold the hollow articles in proper alignment to be stacked with successively discharged articles. When the previously ejected hollow article is not properly aligned in the stacker, the hollow article which is being ejected from the mold or platen, can catch on the previously manufactured cups and both articles can be crushed. With apparatus constructed according to the present invention, the articles, while still in the mold, will be moved into nested relation with the last previously discharged article in the stacker. Accordingly, it is another object of the present invention to provide apparatus of the type described which will minimize the article destruction during the transfer cycle from a differential pressure forming mold to a stack of articles at a stacking station.
It is another object of the present invention to provide apparatus of the type described which will increase the accuracy of alignment of the successively discharged articles at a stacking station.
It is a further object of the present invention to provide mold and trim die apparatus of the type described which will vertically move from a form and trim station to a lowered reoriented position and thence horizontally to move a part into stacking relation with other parts previously discharged to a stacker.
It is another object of the present invention to provide new and novel apparatus for transferring formed and trimmed parts which will enhance the stacking and minimize the part failure.
Another object of the present invention is to provide apparatus of the type described which will move a mold carrying an article, which has been differentially pressure formed therein, to a remote discharge position to be telescopingly received by a previously discharged part in a stacker so that the part is discharged into nesting relation with the previously discharged part.
With the prior art structures, the mold is rotated and brought to a stop before the eject cycle starts. This delay in ejection increases the production time and is relatively inefficient. Accordingly, it is an object of the present invention to provide new, novel, and efficient apparatus which will commence the eject cycle while the mold is being linearly moved relative to a discharge position adjacent the stacker.
During the eject portion of the transfer cycle, the bottom wall of the mold in the aforementioned U.S. Pat. No. 4,565,513 is essentially moved the full length of the mold to completely eject the part from the mold prior to reversing the rotation of the mold. To attain the high ejection velocity required to eject articles from in the prior art illustrated in the U.S. Pat. No. 4,565,513, the bottom mold wall must be moved substantially the entire length of the mold cavity at the stacking station. The extension of the prior art ejector does not commence until after the mold is fully rotated. The retraction of the prior art mold to the forming station does not commence until the bottom wall is retracted which takes substantial time and delays the overall production time. It has been found, according to the present invention, the parts can be ejected while the mold is moving to its final discharge position.
Accordingly, it is another object of the present invention to provide transfer apparatus of the type described which will increase the speed and efficiency of operation by ejecting the parts while the mold is being moved horizontally relative to the stacker.
It is another object of the present invention to provide apparatus of the type described which will discharge a hollow article, having a closed end and an open end, by partially nesting the hollow article being discharged with a previously ejected hollow articles at a stacking station before the hollow article is ejected from the mold.
It is a further object of the present invention to minimize the ejection time inherent in the prior art constructions.
It is another object of the present invention to provide apparatus of the type described which will include a bottom wall of a mold that serves as an article ejector and which will commence movement as the mold is being horizontally moved relative to a stacking station and while being discharged to minimize the distance through which the ejector moves relative to the mold to eject the part.
It is another object of the present invention to provide apparatus of the type described which accelerates and decelerates with cycloidal motion as opposed to very sharp acceleration and deceleration of the prior art.
In the apparatus disclosed in the aforementioned U.S. Pat. No. 4,565,513, the force of gravity, tending to move the mold downwardly, must also be overcome in order to stop rotation of the machine at the discharge station. It has been discovered that it is advantageous to utilize the force of gravity to advantage by converting the linear downward motion of the mold and trim die to rotary motion of the mold and trim die and thus, absorb the rotary energy and reduce the force otherwise required to stop the machine. Accordingly, it is another object of the present invention to provide apparatus of the type described which will convert linear motion energy to rotary motion energy and vice versa to reduce the total energy otherwise required to transfer articles between the mold station and the discharge station.
The path of movement of the mold in the German Publication 1276900 is only arcuate and is not linear at either end. More energy is required to rotate mass and to move it vertically through the same distance. It has been found, according to the present invention, that energy can be conserved by moving the mold linearly to build up linear energy and then transferring or converting the linear energy into rotary energy to at least partially reorient the article being formed to its proper disposition for ejection and then converting the rotary energy to linear energy for linearly transferring the mold transversely in another path to a stacker. Accordingly, it is an object of the present invention to provide apparatus for moving a mold carrying an article part which has been differentially pressure formed therein in a first linear path and then in a transverse linear path and rotating the mold to reorient the mold to different orientations between the paths.
It is a further object of the present invention to provide apparatus of the type described which will move a mold carrying a part in a vertical linear path, horizontally move the mold in a second linear path transverse to the vertical linear path, and reorienting the part as it moves in the first and second paths of travel.
It is a further object of the present invention to provide apparatus of the type described which will linearly withdraw a differential pressure mold and trim die in a first linear, withdrawal path and move the part relative to the mold and trim die as the mold and trim die is moving in a separate linear path transverse to the first linear withdrawal path.
Other objects and advantages of the present invention will become apparent to those of ordinary skill in the art as the description thereof proceeds.